Radiation pneumonitis following multi-field radiation therapy.

The mechanisms of radiation pneumonitis have not been established. In a study on multi-field radiation therapy for lung cancer, one patient developed severe radiation pneumonitis even though the target volume was small. Radiation therapy was performed at a dose of 75 Gy in 50 fractions over five weeks. High-density areas conforming to the radiation field were observed by high-resolution CT. They were observed in the irradiated volume at doses under 20 Gy in the contralateral lung as well as in the ipsilateral lung.